1. Field of the Invention
The invention relates to a method for the equalization of dispersive, linear or approximately linear channels for the transmission of digital signals using a matched filter and a following equalizer and an arrangement for carrying out the method.
2. BACKGROUND INFORMATION
Methods and arrangements of this type are generally used in systems for the transmission of information via dispersive, time-variant channels, particularly radio channels as, for example, in digital audio broadcasting systems (DAB) or in cellular mobile radio systems with dispersive multi-path propagation. Their purpose consists in the receiver-side equalization for the suppression of intersymbol interference, with utilization of multi-path diversity in the abovementioned cellular mobile radio systems.
Known methods of this type, like, for example, the methods described in the articlss by P. Monsen "Feedback Equalization for Fading Dispersive Channels", IEEE Transactions on Information Theory, January 1971, pages 56-64, and D. Godard "Channel Equalization Using a Kalman Filter for Fast Data Transmission", IBM Journal Res. Develop., May 1974, pages 267-273, use decision-feedback equalizers (DFE) which are preceded by a matChed filter (MF) matched to the transmitter.
The main disadvantage of these methods consists in the fact that the adaptation of the receiver is too slow for many applications or can only be implemented with great expenditure.
Other methods, like, for example, the method described in the articles by J. G. Proakis and J. H. Miller "An Adaptive Receiver for Digital Signaling Through Channels With Intersymbol Interference", IEEE Transactions on Information Theory, Vol. IT-15, No. 4, July 1969, pages 484-497, use linear equalizers. The main disadvantage of these methods consists in their poor efficiency, particularly in the case of transmission via rapidly variable channels with high dispersion.
The Viterbi method (G. D. Forney jr. "The Viterbi Algorithm", Proceedings of the IEEE, Vol. 61, No. 4, March 1973, pages 268-278) is also known, in which however, although it is not restricted to linear or approximately linear channels as the abovementioned methods, the signal processing expenditure increases exponentially with increasing duration of dispersion as a result of which the economy of this method is generally greatly limited.
The invention has the object of creating a method of the type initially mentioned, which, with the least-possible signal processing expenditure, provides the possibility of maximum efficiency and fast adaptation of the receiver to the transmission channel, even with long dispersion.